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Climate change, Variability and Fish culture

Akansha Bisht and Grishma Tewari

College of Fisheries

G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India


Aquaculture has been contributing strongly to the growth in fisheries production, contributing to nearly half the fish consumed as food. Aquaculture not only contributes jobs and food but also helps the whole fisheries sector by smoothing out the peaks and valleys of natural production. This keeps prices steadier and enables restaurants and markets to keep their products stable. Production usually concentrates on species with higher prices, such as shrimp, salmon and trout and on species that are easier to produce, such as catfish.

Global change

The natural driving force behind climate change is the greenhouse effect at work in our world's climate systems. As infrared solar radiation from the sun reaches the earth, about 30 per cent of it is reflected back into space, without entering the atmosphere. Another 20 per cent is immediately absorbed into the atmosphere, and the remaining 50 per cent reaches the Earth's surface, where much of it is absorbed and the rest reflected back towards the atmosphere and through to space. The amount of solar radiation that reaches the Earth is about equal to the amount reflected, maintaining an energy balance. Without this greenhouse effect, the environment on Earth would not be favourable to sustaining life.

This energy balance is now being altered by two components of the atmosphere. First, greenhouse gases (GHGs) - the most well-known being carbon dioxide (CO2), methane (CH4), nitrous oxides (N2O), sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs), capture some of the energy reflected from the surface of the earth, keeping it in our atmosphere and warming the planet. Second, aerosols - miniscule particles suspended in the air - primarily have a cooling effect on the Earth because they reflect solar radiation back into space before reaching the atmosphere, though aerosols like black carbon produced from burning of biomass and diesel engine exhaust have a warming effect.

The ocean is also the engine that drives the world's climate, storing huge quantities of solar energy in the process. The ocean absorbs and stores carbon dioxide from the atmosphere. Since this invisible gas is one of the main agents of climate change, the ocean is an important sink that helps to modify human impacts on global climate. Ocean currents, the blue planet's super highways, transfer enormous quantities of water and nutrients from one place to another.

Environmental variability

Environmental variability is a key feature of exploited or pristine ecosystems and has very significant implications for production, development and management of fisheries. The frequency of observed changes and the amplitude of these changes vary widely. Reciprocal influences between natural variation and climate change are not well understood, although it is clear that they both affect fisheries development and management outcomes. Only in the last few years has it become clear that there are climate patterns of a decadal scale that affect production on an ocean basin scale, perhaps even globally for some species.

The ocean is affected by more or less regular natural variations. The primary source of food from the oceans is from capture fisheries and aquaculture. The biological productivity which fisheries exploit varies from place to place and over time in relation to oceanographic conditions which change naturally, from year to year and seasonally. Some natural fluctuations are less frequent, changing only after decades.

Impacts

Climate change impacts are likely to amplify natural variations and to exacerbate existing stresses on marine fish stocks, notably fishing pressure, diminishing wetlands and nursery areas, pollution, and UV-B radiation. In the oceans, climate change is expected to result in increases in sea surface temperature, global sea level rise, decreases in sea-ice cover and changes in salinity, wave conditions, and ocean circulation. On land, climate change, climate change will affect the availability of water, river flow regimes (particularly in flood plains), size of lakes, etc. and the needs of water for other activities competing with fisheries. These changes in turn will have an impact on the biological productivity of aquatic ecosystems and on fisheries. An expected impact of global climate change is an increase in the variability of environmental conditions.

The sensitivity to global change will vary between fisheries. The most affected will be fisheries in small rivers and lakes, in regions with larger temperature and precipitation change and on anadromous species. They will be followed by fisheries within Exclusive Economic Zones, particularly where rigid access regulations reduce the mobility of fishers and their capacity to adjust to fluctuations in stock distribution and abundance, fisheries in large rivers and lakes, fisheries in estuaries (particularly where there are species without migration or spawn dispersal) and in the high seas. 

More specifically for fisheries, climate change-related warming may result in: 

  1. Longer growing seasons and increased rates of biological processes - and often of production; 

  2. Greater risk of oxygen depletion; 

  3. Species shift to more tolerant of warmer and perhaps less-oxygenated waters; 

  4. Redeployment or re-design and relocation of coastal facilities; 

  5. Coastal cultures may need to consider the impacts of sea-level rise on facilities and the freeing of contaminants from nearby waste sites 

  6. Changes in precipitation, freshwater flows, and lake levels

  7. Introduction of new disease organisms or exotic or undesired species 

  8. Establishment of compensating mechanisms or intervention strategies 

  9. A longer season for production and maintenance; and 

  10. Modification of aquaculture systems, e.g. keeping them indoors under controlled light, may be needed more often to protect larvae from solar UV-B. 

Positive impacts

The projected climate change will generally be positive for aquaculture, which is often limited by cold weather. Since many of the changes will involve warmer nights and winters, there should be longer periods of growth, and growth should be enhanced. Also, there should be lower costs from the need to make structures ice-resistant and to heat water to optimum temperatures. .

Possible solutions 

While the fisheries sector cannot do much to impede or seriously affect global climate change, it could contribute to its stabilization or reduction, and to mitigating its effects. Climate changes notwithstanding, there are several actions to consider. The most important strategies are those needed to promote sustainability and which are useful and practical, even in the absence of climate change. Further, when developing strategies, we need to consider both the problems and the opportunities that are being presented, in the following way: 

  1. Active participation at global and regional level, to ongoing debate and collaboration, to obtain the best possible information of fisheries-related impacts 

  2. Allocating research funds to analyze local and regional potential changes in resource magnitude and composition and likely socio-economic impacts

  3. Sharing information obtained with the sector on potential changes, their scale and possible effects on resources and fisheries; 

  4. Establishing institutional mechanisms to enable or enhance the capacity of fishing interests (fleets and other infrastructures) to move within and across national boundaries as a consequence of changes in resources distribution. This implies developing bilateral agreements; 

  5. Preparing contingency plans for segments of the sector that might not be able to move, particularly for disadvantaged areas and small-scale fishers lacking mobility and alternatives; 

  6. Developing effective national and international scale resource management regimes and associated monitoring systems to facilitate adaptation of exploitation regimes in a shifting environment; 

  7. Strengthening regional fisheries management organization and other mechanisms to deal with cross-border stocks; 

  8. Integrating fisheries management into coastal areas management to ensure that fisheries needs are taken up when dealing with protection of coastal areas from sea level rise, etc.

  9. Analyzing aquaculture sustainability in an ecoregional context, forecasting changes in productivity or resistance and in required related changes in culture systems, cultured species or delocalization of productive systems.

  10. Fostering interdisciplinary research, with scientists meeting periodically to exchange information on observations and research results, and meeting with managers to ensure the proper interpretation of results and the relevance of research 

  11. Foreseeing and planning infrastructure adaptations.

Referenes:

Michael H. Glantz (1992). Climate variability, climate change, and fisheries. Cambridge University Press.

Gary Duane Sharp (2003). Future climate change and regional fisheries: a collaborative analysis. Food & Agriculture Org.

L. B. Kli͡a͡shtorin (2001). Climate change and long-term fluctuations of commercial catches: the possibility of forecasting. Food & Agriculture Org- Science.

Chris M. Wood, D. Gordon McDonald (1997) Global warming: implications for freshwater and marine fish. Cambridge University Press.

Julie Kerr Casper (2009). Changing Ecosystems: Effects of Global Warming.Infobase Public.


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